Method of manufacturing tires

ABSTRACT

A method of manufacturing tires includes the steps of making structural components for tires, assembling the structural components of each tire following a pre-established sequence at respective work stations disposed along a manufacturing line, transferring the tires to a curing line, and curing the tires in respective vulcanization molds. The tires are sequentially transferred along the manufacturing line from a first work station to successive work stations. At least one series of tires is simultaneously processed on the manufacturing line and the curing line. The at least one series of tires comprises at least one first tire model and at least one second tire model different from the at least one first tire model. The tires are transferred from the manufacturing line to the curing line at a same rate as the tires are sequentially transferred along the manufacturing line from the first work station to the successive work stations.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication No. PCT/EP00/10443, filed Oct. 24, 2000, in the EuropeanPatent Office, the contents of which are relied upon and incorporatedherein by reference; additionally, Applicants claim the right ofpriority under 35 U.S.C. §119(a)–(d) based on patent application No.99830685.6, filed Oct. 29, 1999, in the European Patent Office; further,Applicants claim the benefit under 35 U.S.C. §119(e) based onprior-filed, provisional application No. 60/173,518, filed Dec. 29,1999, now abandoned, in the U.S. Patent and Trademark Office.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing tyresdifferent from each other, of the type comprising the steps of: making aplurality of structural components for tyres under production;manufacturing the tyres by assembling the components of each of themfollowing a pre-established sequence, at respective work stationsdisposed along a manufacturing line on which tyres being processed arecaused to move by sequential transfer of same from each work station tothe next work station; transferring the manufactured tyres to a curingline; curing the tyres in respective vulcanization moulds associatedwith said curing line.

It is also an object of the present invention an apparatus formanufacturing tyres different from each other, of the type comprising: amanufacturing line having a plurality of work stations, each arranged toassemble at least one respective structural component on a tyre beingprocessed, transfer devices operating along the manufacturing line tosequentially transfer each tyre being processed from a work station tothe next work station; a curing line having vulcanization moulds for themanufactured tyres.

2. Description of the Related Art

A tyre for vehicle wheels usually comprises a carcass structureessentially consisting of one or more carcass plies substantially havinga toroidal conformation and the axially opposite side edges of which areengaged with respective annular reinforcing structures incorporatingcircumferentially inextensible inserts usually called “bead rings”. Eachannular reinforcing structure is incorporated into a so-called “bead”defined along an inner circumferential edge of the tyre for anchoring ofthe latter to a corresponding mounting rim.

Applied to the carcass structure, at a radially outer position thereof,is a belt structure comprising one or more belt strips in the form of aclosed ring, essentially made up of textile or metallic cords suitablyoriented with respect to each other and to the cords belonging to theadjacent carcass plies.

In addition, applied to the belt structure, at a radially outer positionthereof, is a tread band, usually comprised of a band of elastomermaterial of appropriate thickness.

It should be pointed out that, as regards the present description, bythe term “elastomer material” it is meant a rubber blend in itsentirety, i.e. a mixture formed of at least one polymeric base suitablyamalgamated with reinforcing fillers and/or process additives ofdifferent types.

Applied to the opposite sides of the tyre is a pair of sidewalls, eachof which covers a side portion of the tyre included between a so-calledshoulder region, placed close to the corresponding side edge of thetread band, and the corresponding bead.

After the above statements, it is to be noted that each tyre model isessentially distinguishable from the others due to a plurality ofphysico-chemical, structural, dimensional and appearance features.

The physico-chemical features are essentially linked with the type andcompositions of the materials, in particular the recipes for thedifferent blends used in making the elastomer materials. The structuralfeatures essentially define the number and type of the structuralcomponents present in the tyre, and their mutual positioning in the tyrestructure. The dimensional features refer to the geometric measurementsand the profile in right section of the tyre (outer diameter, chord ormaximum width, sidewall height and ratio between the latter, i.e.section ratio) and will be hereinafter merely referred to as “size”. Theappearance features consist of the tread pattern, ornamental motifs anddifferent inscriptions or distinguishing marks reproduced on the tyresidewalls and generally identified as “tread pattern” in the followingof the present description.

The traditional production processes essentially contemplate fourdistinct steps in tyre manufacture: a) preparation of the blends, b)production of the individual structural components, c) assembling of thedifferent structural components in succession to obtain a green carcass,d) curing of the carcass and simultaneous moulding of the tread patternonto the outer surface of the tyre.

In an attempt to reduce production costs, the developing technologyfundamentally addressed itself to the search of technical solutions thatwould bring to achievement of increasingly quicker and more reliablemachinery, so as to minimize time necessary for producing eachindividual tyre, the quality of the finished product being the same oreven better.

Thus plants have been accomplished which have high production capacitiesin terms of number of pieces produced in the time unit, by adoptingmanufacturing machinery having reduced possibilities of modification(i.e. capable of producing only a limited variety of tyre models), butadapted to maximize a mass production of tyres having identicalstructural features. By way of example only, in the most modern plants aproductivity of about two carcasses per minute can be reached.

Attempts have been also made for reducing or eliminating storage of thesemifinished products obtained between two steps in succession of thefour process steps previously listed, so as to minimize costs andinvolved problems each time the tyre model under production is to bechanged. For instance, in document EP 922561 a method of managing tyreproduction is suggested in which, in order to reduce or eliminate astorage time for green tyres and therefore the number of green tyresbeing stocked, arrangement of a curing line having a number of mouldssuitable to constantly absorb the productivity of the manufacturing lineis provided. Production of tyres of different models, in particular ofdifferent sizes, is achieved by replacing and/or adapting each time themachinery arranged in the manufacturing line, concurrently withreplacement of the moulds in the curing line.

It should be recognized however that, at all events, tyre productioninvolves costs that become increasingly higher as the variety of tyremodels to be produced increases: in particular interventions on theprocesses and/or plants for blend production are necessary in order toenable production of components with new and different physico-chemicalfeatures and/or interventions on the production plants for theindividual structural components in order to change the size of thetyres being produced. Change of the operating sequence (differentassembling methodology) and/or the equipment, and adjustment of themanufacturing machinery is also required each time the structure and/orsize of the tyre to be produced has been changed. Finally, availabilityof at least one vulcanization mould for each different “treadpattern-size” pair is required.

The above involves heavy costs for purchasing moulds of different sizesand different tread patterns, as well as different equipment, costs dueto non-saturation of same, losses in productivity due to machinedowntime (changing of a process or equipment generally involves machinedowntime), and machine shop rejections. For instance, in the case ofcontinuously produced components, due to downtime of the downstreamplants and/or change in the component features, an excess in productionis generated that often must be discarded, its reuse being impossible.

Under this circumstance, a person skilled in the art aiming atminimizing costs generally advises against production of a great numberof tyre models on one and the same plant. In fact the cost-minimizingobjective is inconsistent with a frequent change of equipment andproduction processes. Where sale volumes of each model are rather high,there is a tendency to multiply the number of the productive plants soas to make it possible to continuously produce a different model on eachplant, thereby succeeding in minimizing the above drawbacks. On theother hand, where the expected sale volumes for given models are notparticularly high, on an annual basis for example, it is at all eventspreferred to continuously make the whole production of at least one yearimmediately, for the purpose of controlling the production cost. Thissystem however may adversely affect the quality of the product sold andincreases warehouse costs, because the goods are stored for a longperiod of time. In addition, sale risks are increased due for example toan unexpected quick obsolescence of the product, and there is anincrease in financial costs for capital locking up as a result of theproduct remaining in stock and the non-saturation of the moulds that areonly used for the limited period of time required for execution of theestimated reduced volume.

In order to cope with the above problems, the Applicant has already setup a productive method according to which each series of tyres underproduction, identical with each other, is divided into daily batcheseach comprising an amount of tyres adapted to fill the dailyproductivity of the moulds. In this way production of tyres of differentsizes and/or different constructional features is optimized, storage ofgreat amounts of green and vulcanized tyres being eliminated. Thismethod is described in the European Patent Application No. EP 875364 towhich please refer for further possible information.

SUMMARY OF THE INVENTION

In accordance with the present invention, further improvements have beensurprisingly achieved, above all in terms of operating flexibility ofthe tyre-production plant, by carrying out simultaneous working ofdifferent types of tyres both on the manufacturing line and on thecuring line, and performing transfer of green tyres to the curing lineat the same rate as the transfer rate of the tyres themselves betweenthe different stations arranged along the manufacturing line.

In more detail, it is an object of the present invention to provide amethod of manufacturing tyres different from each other, characterizedin that in each of said manufacturing line and curing line at least oneseries of tyres comprising at least one first and one second models oftyres different from each other is simultaneously processed, tyretransferring from the manufacturing line to the curing line beingcarried out at the same rate as the transfer rate of the tyres to eachof said work stations.

Advantageously, production of each structural component is carried outon a manufacturing line by working at least one base semifinishedproduct which is identical for each tyre model, supplied in apredetermined amount depending on the tyre model to be made.

It is further preferably provided that assembling of each structuralcomponent should be carried out before completing manufacture of ahomologous component intended for an immediately following tyre underproduction.

In particular, assembling of the structural components of each tyre ispreferably carried out on a toroidal support the shape of whichsubstantially matches the inner conformation of the tyre itself.

In a preferential embodiment, during the manufacturing step eachtoroidal support is supported and transferred between at least twocontiguous work stations by a robotized arm.

It is further preferably provided that each tyre should be transferredalong the curing line together with the corresponding toroidal support.

Advantageously, accomplishment of at least one of said structuralcomponents is directly carried out on the tyre being processedconcurrently with said assembling step.

In a preferential embodiment, accomplishment of each structuralcomponent is preceded by a step of identifying the model of the tyrebeing processed transferred to the corresponding work station.

In more detail, the identification step is conveniently carried out byreading a code associated with a support member of the tyre beingprocessed.

In at least one of said work stations assembling of a plurality ofstructural components is preferably carried out at respective workingunits.

In addition and advantageously, said manufacturing line extends over aclosed-loop path along which the tyres being processed are caused tomove.

In more detail, the vulcanization moulds are conveniently moved over aclosed-loop path along the curing line, transferring of each tyre to thecuring line being executed after removal of a previously cured tyre.

Advantageously, said at least one first and one second tyre modelsfollow each other in an identical sequence along the manufacturing lineand curing line.

It is a further object of the invention to provide an apparatus formanufacturing tyres different from each other, characterized in thateach of said work stations is arranged to assemble said at least onestructural component selectively on at least one first and one secondtyre model being part of at least one series of tyres beingsimultaneously processed along the manufacturing line, and said curingline comprises at least one series of vulcanization moulds of a numbercorresponding to the amount of tyres included in said at least oneseries of tyres being processed on the manufacturing line, said transferdevices also operating between the manufacturing line and curing line totransfer the manufactured tyres to said curing line, following the sametransfer rate as that for transferring the tyres to each of the workstations disposed along the manufacturing line.

Advantageously, each of said work stations comprises feeding devices tosupply at least one base element for making said at least one structuraltyre component, and application devices for applying said structuralcomponent to the tyre being processed, said structural component beingmade using said base element in a predetermined amount depending on thetyre model to be manufactured.

In a preferential embodiment, associated with each of said work stationsare devices for identifying the model of the tyre being processed in thework station itself, and selection devices to establish the amount ofbase elements to be used for making the structural component of the tyrebeing processed.

In more detail, said identification devices comprise at least one sensordisposed on the manufacturing line and arranged to read at least onecode associated with a support member of each tyre being processed.

In addition, preferably provided is also the presence of a plurality oftoroidal supports each arranged to engage the structural components of atyre being processed.

Advantageously, said transfer devices operate on individual toroidalsupports to sequentially transfer each tyre being processed between thework stations disposed along the manufacturing line, and to the curingline.

In a preferential embodiment, said transfer devices comprise at leastone robotized arm associated with at least one of said work stations.

At least one of said robotized arms preferably comprises grip andcontrol members operating on a toroidal support to hold it up in frontof the respective work station and drive it in rotation around ageometric axis thereof during assembling of said at least one structuralcomponent.

It may be also provided that at least one of said work stations shouldcomprise a plurality of working units, each intended for assembling onerespective structural component to each tyre being processed.

In the presence of a plurality of support members each arranged to holdup one tyre being processed, the transfer devices preferably operate onthe support members to move them alone the manufacturing line followinga closed-loop path.

In a preferential embodiment, the curing line comprises at least oneturntable carrying said vulcanization moulds and operable in rotation ina step-by-step movement to sequentially bring each vulcanization mouldto a loading-unloading station of the tyres being processed.

Said turntable can be conveniently enclosed in an insulating holdingstructure, said transfer devices operating through an access openingarranged in the holding structure itself.

Preferably, the curing line further comprises steam-feeding devicesconnected with a central column of the turntable and leading to theindividual moulds through connecting ducts extending from said centralcolumn.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will become more apparent from thedetailed description of a preferred but nonexclusive embodiment of amethod and an apparatus for manufacturing tyres different from eachother, in accordance with the present invention. This description willbe taken hereinafter with reference to the accompanying drawing, givenby way of example, in which the only FIGURE shows a lay-out of thesubject apparatus, generally denoted by reference numeral 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Apparatus 1 essentially comprises a manufacturing line A on which eachtyre being processed is manufactured by assembling structural componentsof said tyre in a pre-established sequence, and a curing line 3 on whicheach tyre from the manufacturing line 2 is cured within a respectivemould 24, 25, 26, 27, 28, 29.

The manufacturing line 2 essentially comprises a plurality of workstations 5, 6, 7, 8, 9, 10 disposed after each other along amanufacturing path, preferably in the form of a closed loop andrepresented, just as an indication, by arrows 11 in the drawing.

The work stations 5, 6, 7, 8, 9, 10 lend themselves to operatesimultaneously, each on at least one tyre being processed for assemblingat least one of its structural components thereon.

In more detail, during the assembling steps the different structuralcomponents employed in making each tyre A, B, C, D, E, F areconveniently engaged on a support member, preferably consisting of atoroidal support the shape of which substantially matches the innerconformation of the tyre to be obtained. This toroidal support ispreferably of the collapsible type or it is adapted to be divided into aplurality of sectors, so that it can be easily removed from the tyrewhen processing is over.

In accordance with the present invention, both in the manufacturing line2 and the curing line 3, simultaneous processing of at least one firstand one second tyre models is carried out. By way of example, in thelay-out depicted in the drawing, simultaneous processing of sixdifferent tyre models is carried out, which models differ from eachother as regards their dimensional features. However a different numberof models can be acted upon, which models in addition to or as analternative to dimensional differences, may have differences in terms ofstructural and/or physico-chemical features and/or appearance features.

In the diagram shown in the FIGURE, the toroidal supports arerepresented without distinction from the tyres being processed on whichthey are engaged, and they are marked by letters A, B, C, D, E, F,respectively, each letter marring a specific tyre model.

As can be seen, the tyres being processed are distributed along themanufacturing line 2 to form one or more series in each of which thedifferent models A, B, C, D, E, F follow each other in a pre-establishedsequence which is the same for all series. In the example shown, twoseries are distributed along the manufacturing line/and each of themcomprises six tyres A, B, C, D, E, F, different from each other.Therefore, twelve toroidal supports altogether on each of which arespective tyre is manufactured are simultaneously managed on themanufacturing line 2.

It is to be pointed out that in the present description by the term“series” it is meant any assembly of tyres of different models followingeach other in any pre-established sequence. Therefore, in themanufacturing line 2, for example, six series each made up of twodifferent tyre models cyclically coming after each other according tosequence A, B-A, B may be provided, or provision may be made for threeseries each made up of a tyre of a first model alternated with two tyresof a second model, according to sequence A, B, A-A, B, A.

Transfer devices 12, 13, 14, 15, 16, 17, 18 operate on the manufacturingline 2 to sequentially transfer each of the tyres being processed A, B,C, D, E, F from one work station 5, 6, 7, 8, 9, 10, to the next workstation, so as to cause sequential assembling of all tyre components,said tyre being then transferred to the curing line 3.

Preferably, these transfer devices comprise one or more robotized arms12, 13, 14, 15, 16, 17, 18 each of which is associated with at least oneof the work stations 5, 6, 7, 8, 9, 10 and is adapted to operate on theindividual toroidal supports A, B, C, D, E, F to carry out sequentialtransfer of each tyre being processed.

More particularly, in the embodiment shown, a first robotized arm 12 isprovided which is possibly movable along a guide structure 19 andoperates between the manufacturing line 2 and curing line 3, to pick upa finished tyre from the latter and transfer it to a first work station5, where the tyre is removed from the respective toroidal support Athrough disassembling of said support. In the first work station 5, thetoroidal support A is subsequently reassembled to be then transferred,still by the first robotized arm 12, to a stand-by station 20 from whichit will be picked up for subsequent use in the manufacture of a newtyre. In the example shown, in the first stand-by station there is atoroidal support which is ready to process a different tyre model F.

A second robotized arm 13 lends itself to carry out transfer of thetoroidal support F from the first standby station 20 to a second workstation 6 where assembling of the first components for tyre constructionis carried out. In the example shown, in the second work station 6 thetyre being processed is model E. The assembling operation may, forexample, involve coating of the outer surface of the toroidal support Ewith a thin layer of elastomer material impervious to air, usuallycalled “liner”, as well as application of optional elastomer bands closeto the regions corresponding to the tyre beads, and/or formation of anadditional coating layer of elastomer material, placed on top of theliner.

Preferably, in the second work station 6, as well as in the remainingwork stations 7, 8, 9, 10, formation of each structural component of thetyre is carried out concurrently with the above described assemblingstep, by processing at least one semifinished base product, which s thesame for each tyre model A, B, C, D, E, F and is supplied in apredetermined amount depending on the tyre model to be made.

For the purpose, each of the work stations 5, 6, 7, 6, 9, 10 is providedwith one or more working units (not shown), each of which essentiallycomprises feeding devices adapted to supply the required base elementfor accomplishment of the corresponding structural component andoperating in combination with application devices for applying the baseelement and/or the obtained structural component to the tyre beingprocessed.

In particular, in the second work station 6 accomplishment of the liner,the elastomer bands and/or the additional coating layer may beadvantageously carried out by winding up on the toroidal support E beingprocessed, at least one strip-like element of elastomer material havinga width approximately included between 0.5 and 3 cm, to form coilsdisposed consecutively in side by side relationship and optionally alsoat least partly overlapped on each other, said strip-like element comingdirectly from a respective extruder, a reel or equivalent feedingdevices associated with the second work station 6.

Winding-up of coils may be advantageously simplified by entrusting thesecond robotized arm 123 with the task of supporting, by appropriategrip and control members, the toroidal support E, and driving it inrotation around its own axis, suitably moving it in front of pressurerollers or equivalent application devices (not described as they can bemade in any convenient manner by a person skilled in the art) combinedwith the feeding devices, so as to cause a correct distribution of thestrip-like band with respect to the outer surface of the toroidalsupport.

For more details on the modalities of application of the structuralcomponents to a toroidal support with the aid of a robotized arm, pleaserefer to the co-pending European Patent Application No. 98830762.5 inthe name of the same applicant, content of which is considered as hereincompletely incorporated.

When assembling of the components in the second work station 6 has beencompleted, the second robotized arm 13 lays down the toroidal supportwith the respective tyre which is being manufactured in a secondstand-by station 21 that in the FIGURE is occupied by a D-model toroidalsupport, previously processed in the second station itself.

A third robotized arm 14 picks up the toroidal support D from the secondstand-by station 21 to transfer it to a third work station 7, whereassembling of the structural components cooperating in forming thestructure of the tyre carcass is carried out.

In more detail, in the third work station 7 manufacture and assemblingof one or more carcass plies is carried out, as well as of a pair ofannular reinforcing structures for the regions corresponding to the tyrebeads. In the same manner as said with reference to the operating stepsexecuted in the second work station 6, each of these structuralcomponents is directly made during the assembling step, using asemifinished base product supplied in a pre-established amount dependingon the model of the tyre being processed.

For instance, the carcass ply or plies can be formed by sequentiallylaying down or the toroidal support, a plurality of strip-like sectionsindividually cut from a continuous strip-like element made up ofrubberized cords parallel to each other. Each annular reinforcingstructure can, in turn, comprise a circumferentially inextensible insertconsisting for example of at least one thread-like metal element woundup in several radially-superposed coils, as well as a filling insert ofelastomer material to be obtained by application of an elongatedelastomer element wound up to form several coils disposed in axial sideby side relationship and/or in radial-superposition relationship.

Each of said continuous strip-like element, thread-like metal elementand elongated elastomer element forming the semifinished base product tobe used in a pre-established amount for manufacture of the respectivestructural component may directly come from an extruder, a reel orequivalent feeding devices associated with the third work station 7.

For further explanations as regards the manufacture modalities of thecarcass structure, please refer to the European Patent Application No.98830472.1 in the name of the same Applicant, content of which isconsidered as herein completely incorporated.

In the diagram in the FIGURE the third work station 7 is arranged tomake carcass structures for very high-performance tyres, in case ofneed, as described in the European Patent Application No. 98830662.7 inthe name of the same Applicant as well. The carcass structure describedin this patent application comprises two carcass plies each made up of afirst and a second series of strip-like sections laid down on thetoroidal support in an alternate sequence. Also arranged in each tyrebead is a pair of annular reinforcing structures of the previouslydescribed type, each inserted between the end flaps of the sectionsbelonging to the first and second series respectively and forming one ofthe carcass plies, as well as an inextensible insert externally appliedwith respect to the second carcass ply.

To facilitate sequential assembling of the different structuralcomponents following the pre-established order, the third work station 7is provided to be equipped with at least three different working unitsintended for laying down the strip-like sections, thread-like metalelement and elongated elastomer element respectively, and eachsimultaneously operating on a respective tyre being processed. As aresult, in the third work station 7 three tyres A, B, C will besimultaneously processed, each of them being sequentially transferredfrom one of the working units to the other, until completion of thecarcass structure. Sequential transferring of the tyres to the differentworking units arranged in the third station 7 can be carried out by thethird robotized arm 14, optionally with the aid of a fourth robotizedarm 15 and/or possible auxiliary transfer devices.

When accomplishment of the carcass structure has been completed, thefourth robotized arm 15 lays down the toroidal support on a thirdstand-by station 22 that in the FIGURE is engaged by an F-model toroidalsupport

A fifth robotized arm 16 picks up the toroidal support F from the thirdstand-by station 22 to carry it to a fourth work station 6 that in theexample shown is occupied by an E-model toroidal support. In the fourthwork station 8 manufacture and assembling of the structural componentsadapted to define the so-called belt structure of the tyre are carriedout. In particular, a first working unit arranged in the fourth workstation 8 makes, directly on the previously formed carcass structure,two under-belt bands circumferentially extending in the shoulder regionsof the tyre. These under-belt bands can be directly extruded from anextruder and applied with the aid of pressure rollers or equivalentapplication devices.

A second working unit forms a first and a second belt layers on thecarcass structure, each layer being formed by sequential deposition ofribbon-like sections disposed circumferentially in side by siderelationship and each obtained by cutting to size a continuousribbon-like element made up of a plurality of cords disposed parallellyin side by side relationship and incorporated into an elastomer layer. Afurther working unit causes formation of a further belt layer by windingup a continuous cord in coils disposed in axial side by siderelationship and in radial superposition with the underlying beltlayers.

Further details on a possible modality for manufacture of the beltstructure are described in the European Patent Application No.97830633.0 in the name of the same Applicant, to be considered as hereincompletely incorporated.

When manufacture of the belt structure has been completed, the fifthrobotized arm 16 transfers the tyre being processed to a fifth workstation 9 that in the example shown is occupied by a D-model toroidalsupport.

In the fifth work station 9 the toroidal support D is engaged by a sixthrobotized arm 17 with the aid of which application of a tread band iscarried out, said tread band being obtained by winding up a furtherelastomer ribbon-like element in coils disposed consecutively in side byside relationship and superposed until achievement of a tread band ofthe desired conformation and thickness.

The tyre is subsequently transferred to a sixth work station 10,occupied in this example by a C-model toroidal support. In the sixthwork station 10 the toroidal support C is engaged by a seventh robotizedarm 18 causing appropriate handling of same in front of respectiveworking units to carry out application of abrasion-resistant elements tothe regions corresponding to the beads, as well as application of thesidewalls, which can be also obtained by winding up at least oneelastomer band to form coils disposed in side by side and/or superposedrelationship.

When this operation is over, the seventh robotized arm 18 lays down themanufactured tyre on an end stand-by station 23, occupied, in thisexample, by a B-model toroidal support, before transfer of the tyreitself to the curing line 3.

In the light of the above it is well apparent that, due to theprocessing modalities of the individual tyres A, B, C, D, E, F along themanufacturing line 2, assembling of each structural componentadvantageously takes place before manufacture of a homologous component,intended for a tyre A, B, C, D, E, F under production coming immediatelyafter it, has been completed. Due to this preferential feature of theinvention, advantageously tyre manufacture takes place in the completeabsence of semifinished products to be kept in stock and consequently animmediate adaptation of each working unit to the tyre model A, B, C, D,E, F each time transferred to the respective work station 5, 6, 7, 8, 9,10 can be carried out, without involving any material waste.

It should be also pointed out that operation of each of the workingunits arranged in the individual work stations 5, 6, 7, 8, 9, 10, aswell as of each of the robotized arms 12, 13, 14, 15, 16, 17, 18 ismanaged by at least one programmable electronic control unit capable ofsuitably controlling the amount of the delivered semifinished baseproducts and the movements imposed to the toroidal support in order toensure correct formation of the individual structural components of thetyres A, E, C, D, A, F being processed. In particular, this electroniccontrol unit can be programmed in such a manner that operation of theworking units of the robotized arms can be adapted to the tyre model A,B, C, D, E, F, each time processed in each individual work station 5, 6,7, 8, 9, 10.

To give more operating flexibility to the plant, so that it is not boundto predetermined sequences of different tyre models, devices foridentifying the tyre model being processed are preferably provided to beassociated with each of the work stations 5, 6, 7, 8, 9, 10, saididentification devices cooperating with selection devices fordetermining the amount of base elements to be used for making eachstructural component in the concerned work station. For instance, theseidentification devices can advantageously be comprised of a bar code orother code type reader associated with the toroidal support of the tyreA, B, C, D, E, F, interfaced with the electronic control unit todetermine selection of the amount of semifinished products depending onpreviously keyed in value tables. Consequently, as soon as a tyre A, B,C, D, E, F is transferred to any of the work stations 5, 6, 7, 8, 9, 10,the bar code reader identifies the model to which the tyre itselfbelongs, thus enabling the electronic control unit to conveniently setthe operating program of the work station itself.

The curing line 3 advantageously comprises at least one series ofvulcanization moulds 24, 25, 26, 27, 28, 29 of the same number as theamount of tyres included in said at least one series of tyres A, B, C,D, E, F being processed on the manufacturing line 2. In the exampleshown, six vulcanization moulds 24, 25, 26, 27, 28, 29 are provided,each of them corresponding to the size of one of the tyre models A, B,C, D, E, F manufactured along the manufacturing line 2.

Preferably, moulds 24, 25, 26, 27, 28, 29 are mounted on a turntable 30to be driven in rotation in a step-by-step movement in the directionstated by arrow 31, so as to make the moulds carry out a closed-looppath alone the curing line 3, sequentially carrying them, one after theother, to a loading-unloading station 32 of the tyres being processed.

Moulds 24, 25, 26, 27, 28, 29 are each fed with steam under pressurethrough a respective connecting duct 33 radially extending from acentral column 34 into which steam-feeding devices consisting forexample of a boiler are integrated or otherwise connected. The wholeturntable 30 can be advantageously enclosed within an insulatedstructure 35 having at least one access opening disposed at theloading-unloading station 32, so as to avoid excessive heat losses tothe outside.

Advantageously, transfer of the individual tyres being processed A, B,C, D, E, F to the respective moulds 24, 25, 26, 27, 28, 29 is carriedout by the transfer devices at the same rate as that for transferringthe tyres themselves to each of the work stations 5, 6, 7, 8, 9, 10,distributed along the manufacturing line.

For the purpose, starting from the situation depicted in the FIGURE,turntable 30 carries out a rotation step to bring mould 25, adapted toreceive a B-model tyre disposed in the end stand-by station 25, so theloading-unloading station 32.

The first robotized arm 12, after transferring the toroidal support,model A, to the first stand-by station 20, picks up from mould 25, thecured tyre B together with the respective toroidal support to lay itdown into the first manufacturing station 5 for the purpose of removingit from said toroidal support. The first robotized arm 12 then picks upthe green tyre B from the end stand-by station 23 together with therespective toroidal support to transfer it into the correspondingvulcanization mould 25. Mould 25 is closed and fed with steam underpressure through the respective connecting duct 33, to submit tyre B tothe curing step. Cyclic repetition of these operations causes aplurality of tyres A, B, C, D, E, F of different models to besimultaneously processed on the curing line, said tyres following eachother at the same sequence than that detectable along the manufacturingline 2.

From the above description it is apparent that according to the subjectmethod and apparatus, handling of tyres A, B, C, D, E, F being processedis advantageously managed in the form of a continuous flow where themanufacturing line 2 is directly connected with the curing line a,causing sequential transfer of the individual tyres A, B, C, D, E, F atthe same rate as that of transfer of said tyres between the differentwork stations 5, 6, 7, 8, 9, 10 on the manufacturing line 2, therebyadvantageously eliminating the necessity to accumulate green tyres instorage units arranged between the manufacturing line and curing line.

The tyre transfer rate will be determined on the basis of the workingtime employed for completing assembling of the respective structuralcomponents by the working units operating in the individualmanufacturing stations 5, 6, 7, 6, 9, 10, or at all events the workingunit that, as compared with the others, requires the longest period oftime for terminating the assembling operations for which it is intended.

On the whole, said working time and consequently the transfer rate areestablished depending on the number of movement steps provided along thecuring line 3, so that each tyre A, B, C, D, E, F may stay in the curingline itself at least for a period of time sufficient to complete thecuring process.

Just as an indication, in the example shown where six vulcanizationmoulds 24, 25, 26, 27, 28, 29 are provided, the working time andtransfer rate may be provided to have a value in the order of 25minutes, so that each mould will stay in the curing line a timecorresponding to about 15 minutes, during which it will travel along thewhole curing line 3 carrying out six movement steps. If required, thereal time of the vulcanization process carried out on the individualtyres A, B, C, D, E, F may be at all events reduced, by for exampledelaying steam admission to the mould 24, 25, 26, 27, 26, 29 after thetyre has been introduced thereinto. It is therefore advantageouslypossible to establish real vulcanization times different from each otherfor the different tyre models.

The present invention also enables downtime to be eliminated or at allevents minimized, every time replacement of a tyre model underproduction is carried out.

In fact, in this case, only replacing of the toroidal supports andvulcanization mould adapted for production of a model with toroidalsupports and vulcanization mould adapted for production of the new modelis required. This replacing operation, which on the other hand is onlynecessary when there is a change in the dimensional features and/or thetread pattern, has a minimum impact on productivity, not exceeding thenon-production of one tyre. This is in fact the time required to enablea mould to be replaced in the curing line, making the mould itself carryout a “loadless” cycle in the curing line and the manufacturing line,respectively.

Therefore the invention also makes it possible to produce tyres inbatches of very small amounts, even a few units, in a convenient manner,without involving important increases in the unit cost of the tyresthemselves.

1. A method of manufacturing tyres, comprising: making a plurality ofstructural components for tyres; assembling the structural components ofeach tyre following a pre-established sequence at respective workstations disposed along a manufacturing line; transferring the tyres toa curing line; and curing the tyres in respective vulcanization moulds;wherein assembling each structural component is carried out on atoroidal support, wherein a shape of the toroidal support substantiallymatches an inner conformation of a respective tyre, wherein the tyresare sequentially transferred along the manufacturing line from a firstwork station to successive work stations, wherein at least one series oftyres is simultaneously processed on the manufacturing line and thecuring line, wherein the at least one series of tyres comprises at leastone first tyre model and at least one second tyre model different fromthe at least one first tyre model, wherein the tyres are transferredfrom the manufacturing line to the curing line at a same rate as thetyres are sequentially transferred along the manufacturing line from thefirst work station to the successive work stations, and wherein duringassembling the structural components, a corresponding toroidal supportis supported and transferred between at least two contiguous workstations by a robotized arm.
 2. The method of claim 1, wherein eachstructural component is made on the manufacturing line by working atleast one base semifinished product, wherein the at least one basesemifinished product is identical for each tyre model, and wherein theat least one base semifinished product is supplied in a predeterminedamount depending on the tyre model being manufactured.
 3. The method ofclaim 2, wherein making a given structural component is preceded byidentifying a model of the tyre being transferred to a correspondingwork station.
 4. The method of claim 3, wherein identifying the model iscarried out by reading a code associated with the toroidal support ofthe tyre being manufactured.
 5. The method of claim 1, wherein duringassembling the structural components, a given structural component of afirst tyre is assembled before completing the making of a homologousstructural component for a second tyre following the first tyre alongthe manufacturing line.
 6. The method of claim 1, wherein each tyre isassembled on a toroidal support, wherein an inner conformation of eachtyre substantially matches a shape of a corresponding toroidal support,and wherein each tyre is transferred to the curing line together withthe corresponding toroidal support.
 7. The method of claim 1, wherein atone or more work stations, more than one structural component isassembled, and wherein the more than one structural component isassembled at respective working units of the one or more work stations.8. The method of claim 1, wherein the manufacturing line extends over afirst closed-loop path.
 9. The method of claim 8, wherein the curingline extends over a second closed-loop path, and wherein an uncured tyreis transferred to the curing line after removing a previously-cured tyrefrom the curing line.
 10. The method of claim 1, wherein the at leastone first tyre model and the at least one second tyre model follow eachother in an identical sequence along the manufacturing line and thecuring line.
 11. The method of claim 1, wherein at least one of thestructural components is made directly on the tyre being manufacturedconcurrently with the step of assembling the structural components. 12.The method of claim 1, wherein making each structural component iscarried out concurrently with assembling that structural component.